Probability Calculator

Basic events • Permutations & Combinations • Binomial • Bayes

1) Basic Events

Enter probabilities between 0 and 1. If events are independent, tick the checkbox to auto-compute P(A∩B)=P(A)·P(B).

P(A)

P(B)

P(A∩B) (optional)

Treat A and B as independent

n (total items)

k (chosen items)

Formulas: nP_k=n!/(n−k)! • nC_k=n!/[k!(n−k)!]

X ~ Binomial(n, p). Compute point probability and optional cumulative range.

n (trials)

p (success prob)

k (exact successes)

Cumulative: from k₁

Cumulative: to k₂

P(X=k)=C(n,k) p^k(1−p)^n−k • E[X]=np, Var[X]=np(1−p)

Posterior P(A|B)= [P(B|A)P(A)] / [P(B|A)P(A) + P(B|¬A)(1−P(A))]

P(A) (prior)

P(B|A) (likelihood)

P(B|¬A) (false positive rate)